This invention relates to a magnetic separation device which separates material suspended in a liquid using magnetic force.
A magnetic separation device is a device which separates material suspended in a liquid using magnetic force. Because there is no need to change filters in a magnetic separation device, separation of suspended material can be performed continuously without interruption. Consequently, maintenance of a magnetic separation device is easy.
The Japanese Patent Application Laid-Open No. Hei9-248483, published by Japan in 1997, and the Japanese Patent Application Laid-Open No. Hei10-244424, published by Japan in 1998, disclose a magnetic separation device, comprising a pair of rotating plates which rotate while submersed in the liquid and a pair of magnets mounted so as to oppose each of the rotating plates, and which separates material suspended in the liquid by magnetic adhesion to the rotating plates.
Japanese Patent Application Laid-Open No. Hei9-248483 discloses a magnetic separation device comprising a yoke 42 formed in a xe2x80x9cUxe2x80x9d shape, connecting the rear surfaces of two magnets 41 in mutual opposition, as shown in FIG. 7. In this magnetic separation device, when the magnets 41 provided as a pair are within the range over which the magnetic action of one magnet extends to the other magnet, a magnetic circuit is constituted within the yoke 42, and a strong magnetic field occurs between the magnets 41. As a result, the rate of magnetic adhesion of suspended material is increased.
However, in this device, if the magnets 41 provided in a pair are removed to a distance from each other so that the magnetic action from one magnet does not extend to the other magnet, as shown in FIG. 8, a magnetic circuit is not constituted within the xe2x80x9cUxe2x80x9d-shaped yoke 42. Consequently the magnetic field created between the magnets 41 is weakened, similarly to the case of separate individual magnets, and the rate of magnetic adhesion of suspended material is reduced.
Also, because a plurality of xe2x80x9cUxe2x80x9d-shaped yokes 42, each provided with a pair of magnets 41, are positioned parallel to the shaft of rotation of a rotating plate, the product cost tends to be increased, and the increased weight of movable parts tends to result in increased running costs.
Hence an object of this invention is to provide a magnetic separation device with a simple construction and enabling high rates of magnetic adhesion.
In order to attain the above object, this invention provides a magnetic separation device comprising two rotating plates which are fixed to a rotation shaft and rotate while immersed in liquid, and a plurality of magnets mounted on each of the rotating plates, and which causes material suspended in the liquid to magnetically adhere to each of the rotating plates and to be separated from the liquid.
In this magnetic separation device, each of the above magnets is provided with a yoke enclosing the magnet, and having an aperture facing one magnetic pole of the magnet. The yoke comprises an aperture side face, which contacts one of the two rotating plates together with the magnetic pole. A pair of magnets is positioned such that opposite magnetic poles face each other across two rotation plates, so that a magnetic space is formed between the two rotating plates.
More preferably, a xe2x80x9cUxe2x80x9d-shaped groove is formed in the aperture side face of the above yokes. Still more preferably, the magnetic separation device comprises a scraper which scrapes away magnetic material adhering to the above rotating plates, a mechanism which rotates the above scraper in synchronization with the above rotating plates, and means for guiding such that the above liquid flows in the above magnetic space. It is also preferable that the surfaces of the above rotating plates have the property of repelling the liquid.
By means of this invention, a magnetic circuit is constituted in the yoke enclosing the magnet, so that the magnetic field is concentrated at the magnetic pole surfaces, and in addition a magnetic field, of magnitude substantially equal to that at the magnetic pole surface, can be generated at the aperture side face as well.
The yoke is formed into a cup shape enclosing each of the magnets and is mounted onto each of the rotating plates, so that compared with the above-described conventional magnetic separation device in which a xe2x80x9cUxe2x80x9d-shaped yoke is positioned spanning two magnets, the amount of use of yokes in the magnetic separation device of this invention is greatly reduced. As a result, the weight of the magnetic separation device can be reduced and product costs can be lowered, and in addition, running costs can be reduced through the reduction in weight of movable parts.
By forming a groove in the aperture side face of the yoke, the magnetic gradient is heightened in the angular portions of the groove, so that large amounts of magnetic material can adhere.
The details and other features and merits of this invention will be made clear in the remainder of the specification, and will be illustrated in the attached drawings.